The bank's acquisition of the stake in newly created Future Energies Investissement Holding (FEIH) is the first move in a partnership with GDF. The companies said it aims to expand the subsidiary's wind holdings.
FEIH was created as a vehicle to bring together all of the wind assets wholly-owned by GDF, to enable Credit Agricole's investment.
The portfolio includes the 75MW Germinon-Velye project in north eastern France and the 33MW Landes de Couesmé wind farm in Brittany, both of which came online in 2012.
GDF has a target of increasing its total onshore wind capacity in France to 2GW by 2016, up from the 1.2GW it operates today.
The company, which is partially owned by the French state, will maintain its role in the development, construction and operation of present and future wind farms, it said.
The completion of the transaction is expected in the first quarter of 2014.
GDF has been struggling to bring its EUR 34 billion of debts under control, and, while financial terms weren't disclosed, it said that the sale would reduce how much it owed by EUR 400 million.
The energy company announced in July that it was looking to raise EUR 600 million from selling off chunks of its wind portfolio.
In November, GDF made a move towards developing an offshore portfolio when it led a consortium that submitted bids to French energy regulator CRE for the 1GW second offshore wind tender.